Saturday, July 12, 2014

Here is another setup guide that shows how to measure PH using the Dormant Labs PH Module V2, except this time we will calibrate using 10 & 7 ph calibration solutions.

You will need

10 ph calibration solution

7 ph calibration solution

Dormant Labs PH Module V2

A PH probe

4 dupont female to male cables

An Arduino

Containers to hold the PH calibration solutions, and a container to rinse the ph probe with water.

Fill one cup with 10 PH calibration solution, one cup with 7 ph calibration solution, and one cup with water.

Connect the ph probe to the module.

Connect the module SDA,SCL pins to the Arduino SCL and SDA pins, here because we are using a mega, the SCL is pin 21, and SDA is pin 20. Then connect VCC to 5v on the arduino mega, and then connect GND to the GND pin on the arduino mega.

Hello there is no advantage of calibrating with 7&10 vs 4&7. This is because the ph probe response is very very linear. However some people are still losing sleep over it and emailing me about it so I made this tut.

Right now you probably have to assemble one.Here are some ideas:http://bf-arduinolab.wikidot.com/blog:8http://www.kerrywong.com/2012/10/08/i2c-multiplexer-shield-testing/http://forum.arduino.cc/index.php/topic,110115.0.html

You might be able to do it in software:http://www.reddit.com/r/arduino/comments/1ewi10/how_can_you_connect_two_hmc5883l_magnetometers_to/

3) What are major difference between yours and phidget 1130 sensor / atlas scientific (leaving cost)

4) Does this device work out of the box (no calibration needed)

5) How often do we need to calibrate this thing

6) Mostly people calibrate their devices with 3 solutions namely 4.xx 7.xx and 10.xx but yours only 2 so ca we add functionalty for 3 calibration storage ? do you have the arduino code for that ? if not can you make and upload one ?

7) Don't you think it will be better to add this commanly used thing to the device

1) I do not have the resources to do this, but if someone volunteers I could provide them with a ph module.2) The ph module needs to always be calibrated before use, so these tests arent really relevant.3) The phidgets from what I see only works with a phidgets board, and I do not know about the atlas scientific, besides that it doesnt have galvanic isolation last I checked.4) It will work but the readings it puts out will most likely be wrong if you do not calibrate.5) If you are working with water, then probably once a year. It depends on what your ph probe is exposed to.6) You can add it, but it makes such an insignificant improvement vs two point calibration.7) a)No, because people take this module and use it as a piece in their system, and since they are all using it for a different purpose, there isnt an one size fits all approach unfortunately.

1) Do you think if we use it 24/7 than in that case when should we calibrate ?2) Why the Documentation page (on tindie) diverts to 2014/4 blog entry rather than redirecting to this (2014/07) page ?3) On which basis the Ph is compensated ? water temp or room temp ? and i also heared that sometime water temp is important ? can you please elaborate because it is so confusing suppose my temp is 30 deg c (room) and my water temp is 28deg c (reserviour) than what should be used as calculation or the Anrduino automatically does that for you ?

4) I have 4.xxx and 6.xxx (calibration solution) will it work for calibration this device?5) There is an ic which does the Multiplexing of I2C on UNO so you can attach multiple i2c connection over it. Have to got any other idea for doing it (simple one)?6) Can you suggest pH probe (CHEAP ONE)...

Sorry so many mistake in the post here is the correction ...1) Can we use this device 24/7 if yes than how often should we need to calibrate it?2) Why the Documentation page (on tindie) diverts to 2014/4 blog entry rather than redirecting to this (2014/07) page ?3) I heared that sometime water temp is important (i know you use room temp for compensate) ? can you please elaborate because it is so confusing suppose my temp is 30 deg c (room) and my water temp is 28deg c (reserviour) than what should be used as calculation or does the Anrduino automatically does that for you (due to source code)?

4) I have 4.xxx and 6.xxx (calibration solution) will it work for calibrating this device?5) There is an ic which does the Multiplexing of I2C on UNO so you can attach multiple i2c connection over it. Do you got any other idea for doing it (simple way maybe)?6) Can you suggest pH probe (CHEAP ONE)...

One more question i can't help it

7)Is it necessary to provide Precise Voltage to arduino so that this device give perfect reading ? if suppose it is on battery and giving 4.5v will it output wrong pH reading ?

1) It depends on the solution you are measuring, something closer to tap water you would have to calibrate maybe once a year, but if you are measuring say sewage then you would calibrate maybe once a week.

2)The documentation page on tindie I checked, it goes to this documentation page, https://www.tindie.com/products/rezahussain/dormant-labs-ph-module-v2/

3) In that case you would hardcode the temp compensation to 28c. If you knew your water temp was constant

4) It will work but you will have to alter the code, you should use 4 & 7 or 7&10 because I have tested and verified that code.

5) I plan to address this issue in v3 of the module if I end up making it, but in v2 this is all you can do.

6) Any of the ones off of ebay are good, they should be around 30$.

7) No, the ph module works internally off of 3.3v, and communicates with the arduino via i2c so no signal will be lost but your arduino may function erratically from 4.5v

1) Can we use this device 24/7 if yes than how often should we need to calibrate it?2) Why the Documentation page (on tindie) diverts to 2014/4 blog entry rather than redirecting to this (2014/07) page ?3) I heared that sometime water temp is important (i know you use room temp for compensate) ? can you please elaborate because it is so confusing suppose my temp is 30 deg c (room) and my water temp is 28deg c (reserviour) than what should be used as calculation or does the Anrduino automatically does that for you (due to source code)?

4) I have 4.xxx and 6.xxx (calibration solution) will it work for calibrating this device?5) There is an ic which does the Multiplexing of I2C on UNO so you can attach multiple i2c connection over it. Do you got any other idea for doing it (simple way maybe)?6) Can you suggest pH probe (CHEAP ONE)...

One more question i can't help it

7)Is it necessary to provide Precise Voltage to arduino so that this device give perfect reading ? if suppose it is on battery and giving 4.5v will it output wrong pH reading ?

Hello BilluBhai - I purchased a board a few months ago. I am measuring PH of pool water and adding acid when needed. I started with a PH probe siliconed in with a thermistor with it. I did not do a good job of this and it leaked. I now went with a ph probe holder screwed into the pool pvc. and changed the temperatire to just be adjusted by reading voltage drop across a variable resistor. In my case this works fine for a couple of reasons, the pool does not move that fast for a pool with thousands of gallons and for most of the season the temp in the pool is between 20 and 32 degrees C and PH nead 7. At these temps, ph error is not much because I am near 25 deg C.

I bought two PH V2 MODULE; sending to Spain was fast and arrived in perfect condition.

I have two probes ph an Atlas Scientific (expensive) and a Ebay probe(very cheap, € 10) , and to calibrate the module, the values of volt7, volt10 and volt4 are always the same as your example, volt7 = 0.6700 , volt10 = 0.3500 and volt4 = 0.9500.

Hello Reza - I hope this is still an active blog. I have a a question about the code you liked above. Specifically around temp compensation. I see the following and do not understand why you are sending the value 10 to the subroutine?

Now I'll explain why temp compensation has to be done at the calibration step. In the calibration step we are establishing how many volts the ph probe puts out per ph unit. In this case we are using 7 and 10 calibration solutions.

Now, temperature doesn't affect the ph when the ph is 7. But temperature does affect every ph measurement that has an absolute distance away from 7 that isn't zero.

For every measurement that is not ph 7, temp compensation needs to be done to find out what the actual ph is.10PH at 25C is 10PH, but step away from 25C, lets say 15C.

Thank you for the info. Yes, I use a pot to adjust for the temp. The temp is pool water and it is almost always different than the ambient air and since it takes a lot to move it I can adjust it once a week or so. I can go a min of about 60 deg f and a max of 90 deg f with it set like i have it now. I tried a thermister but had problems with it leaking.

Hello Reza - I recently replaced my ph probe and recalibrated using 10 and 7 solution. It is measuring a swimming pool's ph. this pool has a salt water chlorine generator. With this system, the ph can only go up without the addition of acid. we do not have acid rain and really not much rain period. over the last week the probe shows me lower and lower readings. the calibration voltages are as follows: volt 7=1.0964 volt10= 0.8208 calibration temp = 26. operating solution temp = 32. I was thinking this weekend titrating the pool water and seeing water the voltage is on the meter and then adding acid and do it again and maybe again and then graph this to extrpolate to 7 and 10 ph and put those numbers in the system. my titrating will not be real accurate because it is just color shades. The range I need to operate in is only 7.5 to 7.8. I am also thinking I have a bad probe. any thoughts? Here is my full code:

1) do a test with the pool water in a glass, and let me know what happens.

The drift in voltage is very likely caused by a shift in the power supply of the unisolated portion of the measuring circuit. If the drift happens in the pool but not in the glass, then the second test is to test the pool with the chlorine generator turned off or disconnected.

It's my suspicion that the chlorine generator is leaking current into the pool which is disturbing the unisolated power supply through the ph probe. But lets see if I am correct first.

probe in plumbing, no pump, no swg 6.6808 1.1258no pump, no swg, probe in plumbing 6.49 >>this is the same measurement with diff values, unless the temp/ph changed the probe values are drifting through this whole range.

probe in plumbing, pump on, no swg 6.63 1.1312probe in plumbing, pump on, swg on 6.62 1.1318>>this suggests that the swg has no effect

If you had two similar values for probe in plumbing, no pump, no swg, then we could conclude that the pump is causing the issue, but we don't. My theory is that the pump was leaking current that damaged the first probe, then the second probe too.

Thank you. The first probe got wet and that is why I got the new probe. The system is grounded. I think i will try another probe and see what happens. If the pump is creating a voltage in the system are there any options you could suggest or maybe a way to test for the voltage?